"""Ketten-Builder: groups Vorlagen into chains based on Aktenzeichen-Suffix references."""

import sqlite3
from collections import defaultdict

from tracker.core.status import compute_status


def build_suffix_references(conn: sqlite3.Connection) -> int:
    """Create referenzen entries for Aktenzeichen-Suffix relations.

    E.g. 0362/2025-1 references 0362/2025 via suffix relation.
    Returns the number of new references created.
    """
    cursor = conn.execute("""
        INSERT OR IGNORE INTO referenzen (quelle_id, ziel_id, typ, konfidenz)
        SELECT child.id, parent.id, 'suffix', 1.0
        FROM vorlagen child
        JOIN vorlagen parent ON child.aktenzeichen_basis = parent.aktenzeichen_basis
        WHERE child.aktenzeichen_suffix IS NOT NULL
          AND parent.aktenzeichen_suffix IS NULL
          AND child.id != parent.id
    """)
    # Also link sequential suffixes: -2 -> -1, -3 -> -2, etc.
    conn.execute("""
        INSERT OR IGNORE INTO referenzen (quelle_id, ziel_id, typ, konfidenz)
        SELECT later.id, earlier.id, 'suffix', 1.0
        FROM vorlagen later
        JOIN vorlagen earlier
          ON later.aktenzeichen_basis = earlier.aktenzeichen_basis
         AND later.aktenzeichen_suffix IS NOT NULL
         AND earlier.aktenzeichen_suffix IS NOT NULL
         AND CAST(REPLACE(later.aktenzeichen_suffix, '-', '') AS INTEGER)
           = CAST(REPLACE(earlier.aktenzeichen_suffix, '-', '') AS INTEGER) + 1
        WHERE later.id != earlier.id
    """)
    conn.commit()
    return cursor.rowcount


def build_chains(conn: sqlite3.Connection) -> int:
    """Build ketten from Vorlagen that share the same aktenzeichen_basis.

    A chain's Ursprung is the Vorlage without suffix (the original).
    Chain members are ordered by suffix number.
    Returns the number of chains created/updated.
    """
    # Find all aktenzeichen_basis values that have at least one entry
    # and where the base vorlage is an antrag, anfrage, or stellungnahme
    rows = conn.execute("""
        SELECT aktenzeichen_basis, COUNT(*) as cnt
        FROM vorlagen
        WHERE aktenzeichen_basis IS NOT NULL
        GROUP BY aktenzeichen_basis
        HAVING cnt >= 1
    """).fetchall()

    count = 0
    for row in rows:
        basis = row["aktenzeichen_basis"]

        # Get all Vorlagen in this chain, ordered by suffix
        members = conn.execute("""
            SELECT id, aktenzeichen, aktenzeichen_suffix, typ, datum_eingang, betreff
            FROM vorlagen
            WHERE aktenzeichen_basis = ?
            ORDER BY
                CASE WHEN aktenzeichen_suffix IS NULL THEN 0
                     ELSE CAST(REPLACE(aktenzeichen_suffix, '-', '') AS INTEGER)
                END
        """, (basis,)).fetchall()

        if not members:
            continue

        ursprung = members[0]

        # Only create chains for antrag/anfrage types (the base should be one)
        chain_typ = ursprung["typ"]
        if chain_typ not in ("antrag", "anfrage"):
            continue

        # Compute status
        status_info = compute_status(conn, ursprung["id"], chain_typ, members)

        # Determine letzte_aktivitaet
        dates = [m["datum_eingang"] for m in members if m["datum_eingang"]]
        letzte_aktivitaet = max(dates) if dates else ursprung["datum_eingang"]

        # Check if chain already exists
        existing = conn.execute(
            "SELECT id FROM ketten WHERE ursprung_id = ?", (ursprung["id"],)
        ).fetchone()

        if existing:
            kette_id = existing["id"]
            conn.execute("""
                UPDATE ketten
                SET typ = ?, thema = ?, status = ?, status_seit = ?,
                    letzte_aktivitaet = ?, vertagungen_count = ?
                WHERE id = ?
            """, (
                chain_typ,
                ursprung["betreff"],
                status_info["status"],
                status_info.get("status_seit"),
                letzte_aktivitaet,
                status_info.get("vertagungen_count", 0),
                kette_id,
            ))
            conn.execute("DELETE FROM ketten_glieder WHERE kette_id = ?", (kette_id,))
        else:
            cursor = conn.execute("""
                INSERT INTO ketten (ursprung_id, typ, thema, status, status_seit,
                                    letzte_aktivitaet, vertagungen_count)
                VALUES (?, ?, ?, ?, ?, ?, ?)
            """, (
                ursprung["id"],
                chain_typ,
                ursprung["betreff"],
                status_info["status"],
                status_info.get("status_seit"),
                letzte_aktivitaet,
                status_info.get("vertagungen_count", 0),
            ))
            kette_id = cursor.lastrowid

        # Insert chain members
        for pos, member in enumerate(members):
            rolle = _determine_rolle(member, pos)
            conn.execute("""
                INSERT OR REPLACE INTO ketten_glieder (kette_id, vorlage_id, position, rolle)
                VALUES (?, ?, ?, ?)
            """, (kette_id, member["id"], pos, rolle))

        count += 1

    conn.commit()
    return count


def _determine_rolle(member: sqlite3.Row, position: int) -> str:
    if position == 0:
        return "ursprung"
    typ = member["typ"]
    if typ == "stellungnahme":
        return "stellungnahme"
    if typ == "bericht":
        return "bericht"
    if typ in ("antrag", "anfrage"):
        return "aenderung"
    return "ergaenzung"